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United States Patent |
5,649,585
|
Nolte
,   et al.
|
July 22, 1997
|
Process for producing fiber composite investment castings
Abstract
At least one preliminary pattern body, which is then used as part of a
pattern or the pattern itself, is produced with fibers and a pattern
material. A ceramic mold is formed around the pattern with a portion of
the fibers having ends embedded into the mold. The pattern material is
removed and finally, metal in liquid, liquid-solid or powdery form is
introduced into the mold, wherein the metal is at least partially
liquefied in the mold when it is introduced in powdery form. This process
allows investment castings having an increased resistance to be produced
with relatively simple casting equipment.
Inventors:
|
Nolte; Markus (Zum Kampe 25, 33104 Paderborn, DE);
Schaedlich-Stubenrauch; Juergen (Vaalserhaagweg 4A, 6291 CN Vaals, NL);
Neussl; Eric (Koelner Weg 13, 50259 Stommeln, DE)
|
Appl. No.:
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397264 |
Filed:
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November 29, 1995 |
PCT Filed:
|
September 10, 1993
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PCT NO:
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PCT/DE93/00836
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371 Date:
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November 29, 1995
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102(e) Date:
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November 29, 1995
|
PCT PUB.NO.:
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WO94/06582 |
PCT PUB. Date:
|
March 31, 1994 |
Foreign Application Priority Data
| Sep 16, 1992[DE] | 42 30 970.0 |
Current U.S. Class: |
164/10; 164/9; 164/97 |
Intern'l Class: |
B22C 009/04; B22D 019/14 |
Field of Search: |
164/97,9,10
|
References Cited
U.S. Patent Documents
4476916 | Oct., 1984 | Nusbaum.
| |
5394930 | Mar., 1995 | Kennerknecht | 164/97.
|
Foreign Patent Documents |
1508655 | Oct., 1969 | DE.
| |
57-68261 | Apr., 1982 | JP | 164/97.
|
58-29564 | Feb., 1983 | JP | 164/97.
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WO89/09669 | Oct., 1989 | WO | 164/97.
|
Other References
Abstract of Japanese Patent Publication 4-089155 Published Mar. 23, 1992.
Abstract of Japanese Patent Publication 4-143063 Published May 18, 1992.
|
Primary Examiner: Batten, Jr.; J. Reed
Attorney, Agent or Firm: Birch, Stewart, Kolasch & Birch, LLP
Claims
We claim:
1. Process for producing fiber composite investment castings, which
comprises:
providing at least one preliminary pattern body which constitutes fibers of
high strength, high rigidity or both high strength and high rigidity
embedded in a pattern material;
forming a gas-permeable ceramic mold on the preliminary pattern body
surface such that at least a portion of the fibers have ends embedded into
the ceramic mold;
removing the pattern material from the fibers of the preliminary pattern
body such that the fibers remain in the ceramic mold by melting off,
burning out or gasifying the pattern material; and
introducing liquid metal into the ceramic mold such that the liquid metal
infiltrates the fibers in order to form the fiber composite investment
casting.
2. The process according to claim 1, wherein the fibers are mineral fibers.
3. The process according to claim 1 or 2, wherein the fibers are in the
form of a bundle of monofilaments, a bundle of multifilaments wovens,
nonwovens, fiberwoven fabrics or fiber parisons with binder bridges.
4. The process according to claim 1 or 2, wherein the pattern material is
wax.
5. The process according to claim 1 or 2, wherein the pattern material is
synthetic resin.
6. The process according to claim 1 or 2, wherein the pattern material is
removed from the preliminary pattern body at the ends or edges such that
bare fiber sections are fixedly embedded into the ceramic mold.
7. The process according to claim 1 or 2, wherein the preliminary pattern
body is adapted to the requirements with respect to the geometry and load
of the investment castings to be produced by corresponding shaping.
8. The process according to claim 1 or 2, wherein a pattern is solely made
of at least one preliminary pattern body.
9. The process according to claim 1 or 2, wherein one or several
preliminary pattern bodies are surrounded by pattern material for the
purpose of forming a pattern.
10. The process according to claim 1 or 2, wherein the pressure in the mold
environment is lowered below the pressure in the mold interior in order to
increase infiltration by the liquid metal into the fibers.
11. The process according to claim 10, wherein the gas-permeable ceramic
mold is inserted into a container in which a partial vacuum is generated.
12. The process according to claim 1 or 2, wherein the pressure in the mold
interior is raised above the pressure in the mold environment in order to
increase infiltration by the liquid metal into the fibers.
Description
FIELD OF THE INVENTION
The invention relates to a process for producing fiber composite investment
castings.
DISCUSSION OF CONVENTIONAL ART
A process for producing investment castings is known, wherein a pattern is
formed by using a pattern material, a ceramic mold is formed around the
pattern, the pattern material is subsequently melted off, burned out
and/or gasified and finally, liquid metal is introduced into the mold.
According to such a process, investment castings of very complex geometry
can be produced. Owing to such a geometry and due to the fact that the
ceramic mold formed according to this process does only resist relatively
low pressures when introducing the liquid metal into the mold, the use of
reinforcing fibers, i.e. the production of fiber composite investment
castings, is not yet in practice.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a process which
permits the production of fiber composite investment castings with
tolerable production expenditure.
In case of a process of the above-mentioned kind, this object is solved,
according to the invention, by producing at least one preliminary pattern
body of fibers and a pattern material, which is then used as part of a
pattern or the pattern itself, then forming a ceramic mold around the
pattern, and subsequently introducing metal in liquid, liquid-solid or
powdery form into the mold, wherein, in case of an introduction in powdery
form, the metal is at least partially liquefied in the mold. Such a
preliminary body offers a far-reaching freedom of design. This means that
the preliminary body can readily be adapted to the casting to be produced.
Thus, the fiber orientation and the material reinforcement in the casting
intended through them can be achieved purposefully at the desired sites.
DETAILED DESCRIPTION OF THE INVENTION
According to the process of the invention, the pattern material is removed
by melting off and/or burning out and/or gasifying and/or releasing.
According to the process of the invention, fibers having special mechanical
and/or physical and/or chemical properties are used. This means that the
fibers can be selected with respect to the respectively desired
properties.
According to the process of the invention, mineral fibers are used as
fibers. These may be Al.sub.2 O.sub.3 or SiC fibers, which, e.g., are 10
.mu.m thick. Handling such fibers may present a danger to health if these
fibers are bare. According to the present process, however, it is possible
to mechanically make up such fibers into preliminary bodies. When handling
these preliminary bodies, these fibers, however, are then enclosed by the
pattern material and do therefore no longer present a danger to health.
According to the process of the invention, the fibers are used in the form
of a bundle of monofilaments or multifilaments, or as wovens, nonwovens or
fiberwoven fabrics, or as fiber parisons. The selection among the
possibilities given herein can be made according to the respective shapes
and requirements of the casting to be produced.
According the process of the invention, wax is used as pattern material.
This pattern material is the one which is used most often and which can,
as a rule, be treated most easily. Only a relatively low energy
expenditure is required to remove it from the mold.
Further, the process according to the invention can be performed such that
synthetic resin is used as pattern material. Due to the selected fibers
and also with respect to the respective three-dimensional shape, this
pattern material can be particularly suited for special applications.
According to the process of the invention, the preliminary body is released
from the pattern material at its ends or edges, and the thus bare fiber
sections, when forming the ceramic mold, are fixedly embedded therein.
Thus, the preliminary body can be placed particularly exactly in the mold
and thus in the casting to be produced.
Further, the process according to the invention can be performed such that
the preliminary body is adapted to the requirements as to geometry and
load of the investment casting to be produced by corresponding shaping.
According to the process of the invention, the pattern is solely made of at
least one preliminary body. This means that the preliminary body can
directly assume the shape of the casting to be produced and need not be
developed further by depositing pattern material. Such a procedure offers
advantages with simple shapes in particular.
According to the process of the invention, one or several preliminary
bodies are surrounded by pattern material for the purpose of forming a
pattern. Also in this manner, a sufficiently precise placing of the
preliminary body or preliminary bodies in the pattern can be achieved.
According to the process of the invention, the pressure in the mold
environment is lowered below the pressure in the mold interior. In
addition thereto or alternatively, the process according to the invention
can be performed such that the pressure in the mold interior can be raised
above the pressure in the mold environment. Due to these pressure
differences, it is assured that the intermediate spaces between the fibers
are completely filled with liquid metal by pressing and/or sucking. The
pressing is performed by the influence of pressure on the liquid metal
located in the mold, the sucking by inserting the gas-permeable mold into
a container in which a partial vacuum prevails.
The process according to the invention does not require a permanent bond in
the form of binder bridges or the like between the fibers, as has so far
been known in the use of preforms. There, such binder bridges of the
preforms impede the metal infiltration. In the process according to the
invention, it is possible to do without such binder bridges because the
fibers in the preliminary body are held by the pattern material until the
mold cavity is closed and the pattern material is removed then.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following part of the specification, several embodiments of the
method according to the invention are described with reference to the
drawings. The figures show:
FIG. 1 a device for producing rod-shaped or block-shaped preliminary
bodies,
FIG. 2 examples of cross sections of such molding bodies,
FIG. 3 an embodiment of a half of an injection molding tool with the
preliminary body being inserted in plan view and side view,
FIG. 4 a further embodiment of a half of an injection molding tool with the
preliminary body being inserted,
FIG. 5 a finished pattern with fiber sections being bare at their ends, and
FIG. 6 the pattern according to FIG. 5, embedded in a shell mold.
SPECIFIC EMBODIMENTS OF THE INVENTION
In FIG. 1, it is shown in schematic form how strand-shaped preliminary
bodies 2 cut to the desired length are formed from "endless" fibers 1. For
this purpose, several fibers 1 are passed through a heated wax bath 4 by
means of rolls and impregnated with wax there so that all individual
fibers 1 are wetted with wax. The thus impregnated wax fiber strand is
shaped into the desired cross section in a heated pattern die 5 and
solidified in a downstream cooling means 6. The thus obtained, initially
"endless" wax fiber preliminary body is cut into the desired lengths by
means of a separating device 3.
FIG. 2 shows some examples of various cross sections of such preliminary
bodies 2. In this manner, profiles with a high package density of the
fibers as well as profiles with a high resistance moment and combinations
thereof can be realized. Further, a two-dimensionally configured
preliminary body 7 is shown in FIG. 2, which, e.g., can be made in the
form of a woven.
FIG. 3 shows an embodiment of a half 8 of an injection molding tool
consisting of two halves. In this half 8, a preliminary body 2 is inserted
around which a pattern 9 is formed. While doing so, the preliminary body 2
projects beyond the pattern 9 with its two ends. After assembling the
injection molding tool, pattern wax is injected through an injection
channel 10 around the preliminary body 2 and thus, the pattern contour is
filled up.
FIG. 4 shows an embodiment of a half 12 of an injection molding tool,
wherein the inserted preliminary bodies 2 do not emerge from the pattern
body. To insert the preliminary bodies 2 in reproducible pattern positions
in the injection molding tool, winding devices can be used. After closing
the injection molding tool, pattern wax is injected here as well, which
encloses the preliminary body or the preliminary bodies so that a pattern
is formed.
FIG. 5 shows a finished pattern with bare fiber ends emerging therefrom.
These ends serve for fixing the fibers 1 in an investment casting mold
shell. The bare fiber sections are surrounded by ceramic slurry and
stuccoing material used in the production of investment casting mold
shells and are thus firmly anchored in the mold shell which is being
formed. Then, the pattern material is melted off, burned out, gasified or
released. When inserting the metal, the fibers thus anchored in the mold
shell cannot be moved out of their predetermined desired position.
Finally, FIG. 6 shows the pattern according to FIG. 5 in an investment
casting mold shell formed of ceramic slurry and stuccoing material.
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